A large number of devices are known for protection against incorrect operation of circuit breakers. Conventional low-voltage circuit breakers generally have an internal locking slide, which is guided internally behind the control panel of the circuit breaker and connects locking mechanisms, insertion openings for drive cranks, pushbuttons, position signaling devices and the like to an internal connection readiness controller, which enables connection only when all the necessary conditions are satisfied. For example, WO 99/56124 A1 discloses a switching device having a locking device as well as a drive device for insertion and withdrawal relative to a withdrawable part rack, in which said devices can be operated only when the switching device is in the disconnected state. A locking slide (locking rod) is guided by use of elongated holes behind a control panel of the switching device, and has a cam element which interacts with a driver of an OFF operating device. The driver and the cam element interact such that, during operation of the locking slide, the OFF operating device is drawn inward and in the process signals to the user that the switching device is locked in the disconnected state.
A further possible way to provide protection against incorrect operation is described in DE 198 43 207 A1, which discloses a control panel for a circuit breaker, which has a user interface with an apparatus which can be retrofitted for locking, concealing and designing control elements. This retrofitting process is achieved by use of a mounting plate, which can be mounted on the control panel, for holding further functional groups, with the mounting plate having attachment apparatuses for two or more additional elements. One such additional element may be a locking mechanism (locking cylinder).
All these known devices are, however, specific to the switch and are switch-dependent, since they are components of the switch and, for example, are removed together with the switch when the switch is removed from the switchgear assembly. When inserting a different switch, it is thus no longer possible to tell what switching state or what locking conditions existed when the switch was removed. If the characteristics do not match, this can lead to danger in the assembly and to the operator.
Thus, conventionally, a circuit breaker is in general locked in the “OFF” position by pushing and locking the disconnection button. The key is withdrawn and the circuit breaker is locked in the OFF state, and cannot be connected. Nevertheless, it is possible for the circuit breaker to be moved and to be removed in the withdrawable part in the “OFF” switch position.